Oscillators such as a crystal oscillator, a Hartley oscillator, a Clapp oscillator, and an astable multivibrator have been conventionally known. Since such a conventional oscillator is vulnerable to noise, countermeasures against noise are required. Therefore, a fluctuation oscillator including a stochastic resonator is known as an oscillator robust against noise.
For example, Patent Literature 1 discloses a fluctuation oscillator in which a plurality of stochastic resonators is connected in a ring shape. Also, Patent Literature 1 discloses a fluctuation oscillator in which a feedback loop is provided between input and output terminals of one stochastic resonator.
However, since the fluctuation oscillator disclosed in Patent Literature 1 is based on the premise that a plurality of stochastic resonators is provided, there is a problem that costs will increase.
In addition, the fluctuation oscillator has a property of oscillating in synchronization with an input signal. Therefore, by causing the fluctuation oscillator to oscillate in synchronization with a weak unknown input signal and monitoring an output signal from the fluctuation oscillator, it is possible to detect characteristics of this input signal (for example, frequency). Here, in order to cause the fluctuation oscillator to oscillate in synchronization with the weak unknown input signal, it is necessary to adjust a circuit parameter of the fluctuation oscillator to an appropriate value. However, since the fluctuation oscillator disclosed in Patent Literature 1 includes a plurality of stochastic resonators, there is a problem that it is necessary to individually adjust parameters of the stochastic resonators and it takes time and effort to adjust the parameters.
In addition, although Patent Literature 1 discloses a fluctuation oscillator in which a feedback loop is provided between input and output terminals of one stochastic resonator, adjustment of intensity of a signal flowing through the feedback loop is not taken into consideration at all. Therefore, the fluctuation oscillator disclosed in Patent Literature 1 has a problem that the circuit parameters cannot be flexibly adjusted and that it is difficult to cause the fluctuation oscillator to oscillate such that the unknown weak input signal can be detected.